Method and apparatus for casting structures

ABSTRACT

An interior mold form is disclosed, which creates arch-shaped hollows inside a cast material. The form may be used to cast the material into structures as strong as solid structures, but having less weight. More efficient use of material saves on material costs. The mold form creates arch-like hollows in two perpendicular directions within the material, to provide strength against stresses in multiple directions. A process of casting, using the mold is described. An exemplary mold formed of polystyrene is applied to concrete casting. Structures, including those cast of concrete, using the mold and process are also disclosed.

FIELD OF THE INVENTION

1. Field

Embodiments relate to structural engineering, and in particular, to casting structures.

2. Related Art

Molds are used to cast structures out of many types of materials. Typical structures, especially those related to construction, are cast as solid pieces. An example of such a process is the casting of structural concrete.

FIG. 1A is a partially exposed view of a typical concrete wall being cast. Mold sides 102, typically plywood sheets, are used to form mold 100. Horizontal re-bar pieces 106 and vertical re-bar pieces 108, which can be tied together with ties 110, are positioned between sides 102. Concrete mix 120 is poured into mold 100 between sides 102, covering re-bar pieces 106 and 108. Thus, a substantially solid concrete structure is formed.

FIG. 1B is a top view of a typical concrete mold. FIG. 1B is a top view of mold 100, with re-bar pieces 106 and 108 positioned roughly between sides 102.

In some construction projects, such as bridges or road structures, “pre-stressed” concrete is made by casting concrete around cables that are held at a tension.

Because typical concrete structures are solid concrete (with the exception of the re-bar pieces), structure strength depends on the thickness of the concrete and the re-bar reinforcement. However, a solid structure is not necessarily the most efficient use of material volume and mass to achieve strength. For example, the base of a tall structure may need to support a great deal of weight, including its own. Thus, what is needed, is a method of casting materials in more efficient shapes, thereby saving material cost and mass, while providing a convenient method of forming structures.

SUMMARY

In some embodiments, one or more interior mold forms are used to displace material inside a structure being cast. The forms are shaped so as to provide structural integrity in the finished structure cast around them.

In some embodiments, an interior mold form having ridges running in one direction on one side is used to fill the center of a structure during casting. In some embodiments, the structure is cast from concrete and the form is made from polystyrene. In some embodiments, the form is set around a re-bar grid.

In some embodiments, the interior mold form has a second set of ridges on its second side. In some embodiments, the second set of ridges and runs in a cross-direction to the first. In some embodiments the ridges have semi-cylindrical or trapezoidal cross sections.

In some embodiments, the form is created by machining out semi-cylindrical ridges with flat walls, separated by troughs, on one side, then on the other side of a sheet of material. In some embodiments, small holes are bored for plastic inserts to hold the form in position. In some embodiments the form is held away from re-bar to allow concrete to flow around the re-bar.

In some embodiments, the resulting concrete structure, having crossed interior arch-like cells, provides strength equivalent to or greater than that of solid concrete, the displacement of concrete by the form saving weight and cost.

In some embodiments, a process of concrete casting includes laying down a layer of parallel re-bar, forming a 3-D polystyrene mold, and providing the mold with plastic spacers to hold it in correct alignment to the re-bar. The form is placed over the first layer of re-bar, a second layer of re-bar is added over the mold, and the re-bar intersections are attached together. The mold and re-bar are held between sides of a mold, and concrete is poured, and allowed to harden. The external mold sides are removed, and the internal form remains in the concrete structure.

In some embodiments, a mold form comprises an array of semi-spherical bumps.

In some embodiments, a mold is created from an exterior volume and an interior mold form.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

FIG. 1A is a partially exposed view of a typical concrete wall being formed.

FIG. 1B is a top view of a typical concrete mold.

FIG. 2A is a side view of an embodiment of an interior mold form, according to the present invention.

FIG. 2B is a side view of an embodiment of an interior mold form, at 90 degrees to FIG. 2A, according to the present invention.

FIG. 2C is a perspective view of an embodiment of an interior mold form and reinforcing bars, according to the present invention.

FIGS. 3A through 3F illustrate an embodiment of a process for casting concrete, according to the present invention.

FIGS. 4A and 4B are cross sections (at right angles) of an embodiment of a concrete structure, according to the present invention.

FIG. 4C is a perspective view of an embodiment of a cast structure, according to the present invention.

FIG. 5 is a perspective view of an embodiment of an interior form with trapezoidal structure, according to the present invention.

FIG. 6 is a perspective view of an embodiment of an interior mold form with bumps within a concrete structure cast in a horizontal inclination, according to the present invention.

FIG. 7 is a perspective view of an embodiment of an interior mold form having ridges on one side within a concrete structure cast in a horizontal inclination, according to the present invention.

DESCRIPTION

FIG. 2A is a side view of an embodiment of an interior mold form, according to the present invention. In some embodiments, form 200 is cut from a thin block (a right rectangular prism) having two large flat faces (sides). Because many structures are walls (or wall-like), it is convenient to describe embodiments of form 200 in terms of constructing walls. However, those skilled in the art will recognize that form 200 can be applied to many different structures of different shapes and sizes.

In some embodiments, form 200 will resemble a relatively thin sheet, having two major sides (surfaces). For purposes of illustration, an x-axis, which will be “horizontal” in some embodiments, is defined along one side of form 200, parallel to its surface. A y-axis, which will be “vertical” in some embodiments, is defined along the other long side of form 200, parallel to that surface, and perpendicular to the x-axis. A z-axis is defined through form 200, being normal to the surfaces (sides). While the terms “horizontal” and “vertical” are used to illustrate embodiments, because typical vertical walls are commonly cast, such terms are not intended as limiting. In application, embodiments of form 200, related processes, and structures in which it is used, may take on many shapes, orientations, and contours, which may or may not be symmetric, planar, or aligned with gravity.

As shown in FIG. 2A (looking along the x-axis at the y-z plane), in some embodiments, one face 201 of form 200 has roughly semi-cylindrical ridges 202 running along the x-axis. The term “semi-cylindrical” is to be broadly interpreted, and includes sections of a cylinder of different lengths and angular extent, as shown in FIG. 2A. Base 203 of each ridge 202 extends the shape of ridge 202 beyond a half cylinder, giving it a cross section, which is roughly a hemisphere with a rectangular base, an arch-shape. In some embodiments, ridges 202 are separated by troughs 204, which also run along the x-axis. Troughs 204 may be different shapes, for example, roughly rectangular or curved around the re-bar.

FIG. 2B is a side view of an embodiment of an interior mold form, at 90 degrees to FIG. 2A, according to the present invention. As shown in FIG. 2B, second face 205 of form 200 has ridges 206 running along the y-direction. Similar to first face 201, ridges 206 have base portions 207, and troughs 208 separate ridges 206. Thus, looking in the z-direction the x and y ridges 202, 206 and x and y troughs 204, 208 cross. In some embodiments, troughs 204 and 208 are deep enough (i.e., bases 203 and 207 are deep enough) such that they intersect inside form 200.

FIG. 2C is a perspective view of an embodiment of an interior mold form and re-bar, according to the present invention. Intersections 220 of x-troughs 204 and y-troughs 208 form holes 220, substantially extending through form 200.

Referring to FIGS. 1, 2A, and 2B, when concrete is to be cast around re-bar 106 and 108, horizontal re-bar 106 lies in troughs 204, and vertical re-bar 108 lies in troughs 208, crossing at intersections 220 of FIG. 2C. Because intersections 220 extend through form 200, re-bar 108 and 106 can be tied (if desired) through intersections 220. In some embodiments wire ties are used. As those skilled in the art will recognize, a tying machine with a long nose can be used to facilitate tying. Those skilled in the art will also recognize that not every intersection of re-bar 106 and 108 needs to be tied.

Referring to FIGS. 2A and 2B, in some embodiments, holes 210 are formed in form 200. In some embodiments, holes 210 are formed by cutting into form 200 along lines 212, because holes 210 may be longer than a conventional drill bit. Holes 210 can be cut along x and y directions or along any other convenient directions through form 200.

In some embodiments, plastic rods 214 are inserted in holes 210 of form 200 to aid in positioning form 200 with respect to re-bar 106 and 108. Plastic rods 214 can stop form 200 from sliding too far onto re-bar 106 or 108. Plastic rods 214 can also supply means of tying form 200 onto re-bar. In some embodiments, rods 214 are not used, and in some embodiments there are fewer rods than pieces of re-bar 106 and 108.

In some embodiments, form 200 is made from 2-lb polystyrene. 2-lb polystyrene has desirable compression (approximately 20 pound per square-inch) and machining properties. Form 200 is stiff enough to resist being crushed by the mass of concrete. Depending on the scale of the casting to be performed other weights of polystyrene may be acceptable, if they provide sufficient compression resistance. In some embodiments, form 200 is made from other lightweight, inexpensive materials, such as fiberglass, composite carbon/graphite, plastic, or other weights of polystyrene. For casting materials other than concrete, form 200 may be formed from materials resistant to adverse conditions during casting (e.g., extreme pressure, chemical damage, high temperatures).

In some embodiments, form 200 is cut from a 3 by 4 by 8-foot block of 2-lb polystyrene. Billets are typically manufactured in 3 by 4 by 24-foot sizes, and 8-foot lengths are convenient to cut from such a billet (also being roughly the size of typical freeway sound barrier segments). Of course, different applications will require different sizes and shapes of concrete castings, so given dimensions are exemplary.

As an example of relative dimensions, in some embodiments form 200 is 3{fraction (9/16)}-inches thick. Ridges 202, 206 (and therefore troughs 204, 208) have a period of 4-inches. Each ridge 202, 206 has a semi-cylindrical diameter of 2{fraction (7/8)}-inches (radius of 1{fraction (7/16)}-inches) and a ⅞-inch base height, for a total height of 2{fraction (1/2)}-inches. Each trough has a width of 1{fraction (1/8)}-inches and a depth of 2{fraction (1/2)}-inches (leaving 1{fraction (1/16)}-inches of material). For a form of these exemplary dimensions, external mold sides 102 are placed so as to create a thickness of {fraction (11/16)}-inch of concrete between each of mold sides 102 and form 200.

FIGS. 3A through 3F illustrate embodiments of a mold and a process for casting concrete, according to the present invention. In FIG. 3A, form blank 200′ is ready to be cut into form 200.

In FIG. 3B, form 200 is shown after ridges 202 and troughs 204 have been machined into it. It has also been provided with plastic rods 214.

In FIG. 3C vertical pieces of re-bar 108 are set up and form 200 is inserted over them. Horizontal re-bar 106 is added, and (if desired) ties 110 are applied.

FIG. 3D shows the completed form and rebar.

FIG. 3E shows the completed form 200 and rebar 106, 108 inserted between mold barriers 102 to form mold 300. Those skilled in the art will appreciate that all sides of mold 300 are sealed with additional plywood, plastic sheets, earth, previously cast sections, or another material to prevent mix 120 from leaking out.

FIG. 3F illustrates material 120 poured into mold 300, around form 200.

While a vertical mold is exemplary, it is well known to those skilled in the art, that walls for concrete buildings can be cast in a horizontal orientation, on the ground, before being raised into a vertical position. In such a process, all the re-bar (and the x- and y-axis) would be literally horizontal during casting and curing. However, it is convenient to refer to re-bar 106 and 108 as being “vertical” or “horizontal,” and such terms are not intended as limiting.

By means of using form 200, a concrete structure can be created, which is lighter than a solid concrete structure of equal size and strength.

Those skilled in the art will recognize that mold 300 and form 200 need not be rectangular; they can be oval or oddly shaped. Further, those skilled in the art will recognize that mold 300 and form 200 need not be planar, although many applications use planar shapes. Given that modern architecture make use of many curved and irregular surfaces, embodiments of form 200, mold 300, and the molding process will make use of forms and molds of many different shapes, sizes, and contours.

Further, those skilled in the art will recognize that while re-bar 106 and 108 are commonly used in concrete structures, re-bar is not essential to all embodiments of casting processes or resulting structures. Therefore, in some embodiments, there is no re-bar. In some embodiments, structure integrity is reinforced by means other than inserting re-bar 106 and 108 (e.g., inserting graphite fibers).

While concrete casting is exemplary of some embodiments of the present invention, those skilled in the art will recognize that embodiments of the forms and processes herein described are also applicable to other materials on larger or smaller scales. Such materials may include structural plastics, graphite epoxies, metals, and many other materials, where it is desirable to reduce the volume of material required to form a structure.

FIGS. 4A and 4B are cross sections of an embodiment of a concrete structure, according to the present invention. FIG. 4A is an x-z view of concrete structure 400. Half 410 of structure 400 can be seen to have chambers 412 running through it in the y-direction. In some embodiments, form 200 is left in-place after casting concrete 120, so that form 200 remains in chambers 412. Similarly, half 420 of structure 400 can be seen to have chambers 422 running through it in the x-direction, also filled with form 200.

While chambers 412 and 422 are not filled with concrete, the arched semi-cylindrical shape of chambers 412 and 422 bear stresses within structure 400 more efficiently than solid concrete. Because chambers 412 and 422 are crossed, each of halves 412 and 422 resists stresses along the different axis. Therefore, the double-arched hollows within structure 400 provide superior strength to solid concrete. Further, by creating structures of lighter weight, each structure in, for example a building, needs to support less weight of itself and other structures, thereby making the entire building more efficiently constructed, than if it were made of solid walls.

FIG. 4C is a perspective view of an embodiment of a cast structure, according to the present invention. As in FIGS. 4A and 4B, it can be seen that structure 400 is formed with interior arches 413 on side 410 running in the y direction and with arches 423 on side 420 running in the x direction.

FIG. 5 is a perspective view of an embodiment of an interior form with trapezoidal structure, according to the present invention. Referring to FIGS. 2-4, some embodiments make use of arch-shaped, semi-circular ridges 202, 206 in form 200, forming arches 412, 423 in structure 400. Interior mold form 500 (shown in FIG. 5) makes use of trapezoidal ridges 502 (having trapezoidal cross-section). Similar to the semi-circular arch shapes in ridges 202, 206 of form 200, the trapezoidal shape of ridges 502 of form 500 also provides strength in the resulting structure. Those skilled in the art will recognize other ridge configurations that may differ in geometry (e.g., geodesic), but which perform the function of providing structure 400 with material strength by providing a stable internal structure.

FIG. 6 is a perspective view of an embodiment of an interior mold form with bumps within a concrete structure cast in a horizontal inclination, according to the present invention. Mold form 600 includes hemispherical bumps 602, which displace material 120 during casting. In some embodiments, mold form 600 is used to cast concrete for roadways. The shape of bumps 602 results in the formation of arches in the resulting structure. In some embodiments, bumps 602 are on one side of form 600. In some embodiments form 600 is used for horizontal structures (e.g., roads, counter-tops), where the structure is designed to bear the vertical stress of objects pressing down on it.

In some embodiments, form 600 includes base 610, having thickness 612. In some embodiments, thickness 612 is made thick enough to provide convenient strength to mold form 600 for handling and transportation. In some embodiments, thickness 612 is very thin, only thick enough to hold bumps 602 in place during casting. In some embodiments thickness 612 vanishes, and bumps 602 are held in place by wires, rods, or other means, or held in place by friction against the surface under them. In some embodiments, bumps 602 are an array of discrete interior forms.

In some embodiments, material 120 is cast around form 600 and re-bar 106 and 108. In some embodiments, lower layer 620 of material 120 has a thickness of approximately 2-inches, form thickness 612 is approximately 2-inches, making form and upper layer 622 of material 120 has is approximately 12 inches thick. Total thickness 624 is approximately 16-inches.

In some embodiments, a structure, such as a roadway, is formed by preparing the ground, then pouring a thin layer of concrete. Form 600, along with rebar 106, is placed on top of the first layer of concrete, and a thicker main layer is poured.

FIG. 7 is a perspective view of an embodiment of an interior mold form having ridges on one side within a concrete structure cast in a horizontal inclination, according to the present invention. In some embodiments, material and weight can be saved by using an interior form 700 with ridges 702 on only one side 704. Provided that the structure cast with form 700 will have sufficient strength for its intended purpose (while having an asymmetric interior structure) mold form 700 is simple to make and will save on material costs. Referring to FIGS. 2A-2B, in some embodiments ridges 702 are semi-circular, arch shaped. Referring to FIG. 5, in some embodiments ridges 702 are trapezoidal. In some embodiments, ridges 702 have other structural cross sections, shapes, or contours.

Thus, embodiments provide strong structures using less material than typical casting.

While various embodiments of the invention have been described, it should be understood that they have been presented by way of example and not limitation. Those skilled in the art will understand that various changes in forms or details may be made without departing from the spirit of the invention. Thus, the above description does not limit the breadth and scope of the invention as set forth in the following claims. 

1. An interior mold form for casting a structure, comprising: a sheet of material, having a first side having a surface and a second side having a surface, comprising: a first plurality of parallel, ridges, disposed on the first side of the sheet, the ridges being parallel to the first side surface
 2. The interior mold form of claim 1, further comprising: a second plurality of parallel ridges, disposed on the second side of the sheet, the ridges being parallel to the second side surface.
 3. The interior mold form of claim 2, wherein the first plurality of ridges and the second plurality of ridges are non-parallel.
 4. The interior mold form of claim 3, wherein the first plurality of ridges and the second plurality of ridges are substantially perpendicular.
 5. The interior mold form of claim 1, wherein the ridges of the first plurality of ridges are roughly semi-cylindrical in shape.
 6. The interior mold form of claim 5, further comprising a second plurality of ridges, roughly semi-cylindrical in shape.
 7. The interior mold form of claim 6, further comprising: a first plurality of troughs, disposed between each ridge of the plurality of ridges; and a second plurality of troughs, disposed between each ridge of the second plurality of ridges.
 8. The interior mold form of claim 7, wherein the first plurality of ridges and second plurality of ridges are non-parallel.
 9. The interior mold form of claim 8, wherein the first plurality of ridges and second plurality of ridges are substantially perpendicular.
 10. The interior mold form of claim 9, wherein the first plurality of troughs and the second plurality of troughs intersect, the intersections of the troughs forming apertures through the sheet of material.
 11. The interior mold form of claim 10, formed of polystyrene or fiberglass.
 12. The interior mold form of claim 10, formed of 2-lb polystyrene.
 13. The interior mold form of claim 6, wherein the first and second plurality of ridges comprise semi-cylindrical segments and roughly flat bases.
 14. An interior mold form, comprising a plurality of arched bumps.
 15. The interior mold form of claim 14, wherein the bumps are arrayed on a planar support.
 16. A mold, comprising: one or more exterior retaining-sides; an interior mold form; and means of securing the interior mold form within the mold.
 17. The mold of claim 16, wherein the interior mold form comprises: a sheet of material, having a first side having a surface and a second side having a surface, comprising: a first plurality of parallel, ridges, disposed on the first side of the sheet, the ridges being parallel to the first side surface a second plurality of parallel ridges, disposed on the second side of the sheet, the ridges being parallel to the second side surface.
 18. The mold of claim 17, wherein the interior mold form further comprises: a first plurality of troughs, disposed between each ridge of the plurality of ridges; and a second plurality of troughs, disposed between each ridge of the second plurality of ridges
 19. An interior molding form, made by a process comprising: a. Providing a sheet of material having a first side and a second side; b. Machining a first plurality of parallel ridges into the first side of the sheet.
 20. The interior molding form of claim 19, wherein the first plurality of parallel ridges are separated by troughs.
 21. The interior molding form of claim 20, wherein the process further comprises: c. Machining a second plurality of parallel ridges separated by troughs on the second side of the sheet.
 22. The interior molding form of claim 21, wherein the first and second plurality of ridges are roughly perpendicular.
 23. The interior molding form of claim 22, wherein the sheet of material is 2-lb polystyrene.
 24. The interior molding form of claim 23, further comprising positioning rods.
 25. An interior mold form for casting a material, comprising: means for displacing the material to be cast, from within the material, for forming a regular interior structure.
 26. The interior mold form of claim 25, further comprising: means for securing the interior mold form within an external mold.
 27. A method for casting, comprising: a. Providing a material to be cast b. Providing an interior mold form, capable of displacing the material to be cast; c. Providing exterior mold sides; d. Forming a mold, comprising the interior mold form, retained inside the exterior mold sides; e. Substantially filling the mold with the material to be cast; and f. Hardening the material.
 28. The method of claim 27, wherein the interior mold form is polystyrene.
 29. The method of claim 28, wherein the material to be cast is concrete.
 30. The method of claim 29, further comprising: g. Positioning reinforcing bars within the mold.
 31. The method of claim 30, further comprising: h. Securing the interior form against the reinforcing bars with plastic rods.
 32. A method for casting a material with internal structure, comprising: a. Providing a volume in which a material to be cast may be retained; b. Providing one or more material displacing forms within the volume; c. Substantially filling the volume with the material to be cast; and d. Hardening the material.
 33. The method of claim 32, wherein the one or more material displacing forms comprise ridges.
 34. The method of claim 33, wherein the one or more material displacing forms comprise polystyrene
 35. A cast structure, formed by the process of: a. Providing an interior mold form; b. Providing an exterior mold side; c. Forming a mold, comprising the interior mold form, retained inside the exterior mold side; d. Substantially filling the mold with a material to be cast; and e. Hardening the material.
 36. The cast structure of claim 35, wherein the interior mold form, comprises: a sheet of material, having a first side surface and a second side surface, comprising: a first plurality of parallel, roughly semi-cylindrical ridges, disposed on the first side of the sheet, having axis parallel to the first side surface; and, a second plurality of parallel, roughly semi-cylindrical ridges, disposed on the second side of the sheet, having axis parallel to the second side surface, and perpendicular to the axis of the first plurality of ridges; a first plurality of troughs, disposed between each ridge of the plurality of ridges; and a second plurality of troughs, disposed between each ridge of the second plurality of ridges.
 37. The cast structure of claim 36, wherein the interior mold form, is formed from one of polystyrene, fiberglass, plastic, or ceramic.
 38. The cast structure of claim 37, wherein the material to be cast is concrete.
 39. The cast structure of claim 38, wherein the process further comprises: f. Providing reinforcing bars within the troughs of the interior mold form.
 40. The cast structure of claim 39, wherein the process further comprises: g. Positioning the interior mold relative to the reinforcing bars to allow the flow of material around the mold and reinforcing bars.
 41. A method for casting a horizontally aligned structure, comprising: a. preparing a flat area of ground for concrete application; b. pouring a first layer of concrete; c. positioning a mold form over the thin layer of concrete; and d. pouring a second layer of concrete over the mold form. 